Is the email I am sending being sent through Gmail or my web host?

Is it correct that the settings I used for setting up my mailing software (ARPreach) with my Gmail account do not use the Google SMTP servers? If so, am I currently sending through my host’s webmail?

Yes, based on the settings you provided, it appears that you are not using the Google SMTP servers for sending emails. Instead, you are sending through the localhost SMTP server on port 25, which suggests you are using your host’s webmail. This means that your emails are being sent from your hosting provider’s server instead of directly from Gmail.